An apparatus and system for subdividing the floor surface of an open space, creating work spaces and enclosed offices with furniture. The system consists of rigid divider panels (21), vertical posts (20) and horizontal rails (25), which combine to form wall segments. These wall segments are interconnected, and arranged to define the desired work space or enclosed office. Various work surfaces are attached by bracket means to the wall segments depending on the intended use of the work space. Additional work spaces can be added later, or the work surfaces may be reconfigured to adapt to the user's changing needs. Cross members (82) may be added to add support to the work space. Lighting means (86) may be hung from the lower surface (87) of the cross members (82). Ceiling panels (88) may be attached to the upper surface of the cross members (82) and horizontal rails (25) to enclose the work space.